To determine whether a hypoperfusion index ratio (HIR) >0.5 is associated with a worse NIHSS score at 24h post-mechanical thrombectomy (MT) and early neurologic decline (END) in large vessel (LVO) versus distal and medium vessel occlusions (DMVO) acute ischemic stroke (AIS).

HIR is a surrogate marker for collateral status and a predictor of infarct growth, malignant cerebral edema, and hemorrhagic transformation. Its utility to predict a poor NIHSS and END after MT for LVO versus DMVO has not been investigated.

This is a retrospective study of 231 AIS patients with LVO or DMVO amenable for MT, and available CT-perfusion for HIR assessment pre-MT. Clinical and imaging characteristics were abstracted from medical records. The primary outcome was NIHSS at 24h post-MT. The secondary outcome was END, defined as >4-point increase in NIHSS between initial assessment and 24h post-MT.

HIR>0.5 was more frequently present in LVO as compared to DMVO group (n=41 [66.1%] vs. n=21 [33.9%]; p=0.037).  On multivariable linear regression, HIR>0.5 was independently associated with a worse NIHSS score at 24h post-MT in the entire cohort (Beta=0.132; p=0.014) and LVO (Beta=0.225, p=0.004), but not in DMVO group. END occurred in 26 (11.3%) subjects. On multivariable logistic regression, there was no association of HIR >0.5 with END in the entire cohort after adjustment. When analyzed separately, HIR>0.5 significantly increased the odds for END in LVO subjects (OR=5.787, 95%CI 1.179-28.515, p=0.031) but not in the DMVO group (OR=0.249, 95%CI 0.009-6.517-28.515, p=0.404).

HIR >0.5 was independently associated with worse 24h post-MT NIHSS and END in LVO, but not DMVO AIS. Further studies are needed to determine whether distinct CTP parameters should be used for outcome prediction and patient selection for endovascular treatment in DMVO.